Regaining Balance & Equilibrium

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  • Balance & Postural Equilibrium

  • Factors impacting balanceMuscular weaknessProprioceptive deficitsROM deficits

  • TerminologyBalance - Process of maintaining bodys CoG within base of supportBodys CoG rests slightly above the pelvisAbility to align body segments against gravity to maintain or move the body within the available base of support without falling (Kisner & Colby, 2002, 4th ed.)Strength is emphasized before proprioception in rehab because strength influences balancePostural equilibrium - broader term that incorporates alignment of joint segmentsMaintaining CoG (Center of Gravity) within the limits of stability (LOS)Proprioception bodys ability to transmit position sense, interpret info & respond consciously/unconsciously to stimulationCoordination smooth pattern of activity is produced through a combo of muscles acting together with appropriate intensity & timingAgility ability to control the direction of a body or segment during rapid movement

  • Postural Control System3 Components of the systemSensory detection of body motionsVisualVestibular Somatosensory inputsIntegration of sensorimotor information within the CNSExecution of musculoskeletal responses

    Balance is both a static & dynamic process

  • Control of BalanceTall body vs. Small base of supportBalance relies on network of neural connectionsPostural control relies on feedback

    CNS involvementSensory organizationDetermines timing, direction & amplitude of correction based on inputSystem relies on one sense at a time for orientationMuscle coordinationCollection of processes that determine temporal sequencing & distribution of contractile activity

  • Sensory InputVisionMeasures orientation of eyes & head in relation to surrounding objectsHelps maintain balanceVestibularProvides info dealing with gravitational, linear & angular accelerations of the head with respect to inertial spaceMinor role when visual & somatosensory systems are operating correctlySomatosensoryProvides info concerning relative position of body parts to support surface & each other

    Somatosensation = Proprioceptive systemSpecialized variation of the sensory modality of touch, encompassing joint sense (kinesthesia) & positionProcessInput from mechanoreceptorsStretch reflex triggers activation of muscles about a joint because of perturbationResults in muscle response to compensate for imbalance and postural swayMuscle spindles sense stretch in agonist, relay information afferently to spinal cordInformation is sent back to fire muscle to maintain postural control

  • Body position in relation to gravity is detected by sensory input

    Balance movements involve a number of jointsAnkleKneeHipCoordinated movement along kinetic chain

  • Prentice, 2004, 4th ed.

  • Balance relating to the CKCKinetic chainEach moving segment transmits forces to every other segmentMaintaining equilibrium involves the closed kinetic chain (foot = distal segment fixed beneath base of support)

    Automatic postural movementsDetermined via indirect forces created by muscles on neighboring jointsSeries of joint strategies are involved to coordinate movementInjury to joints or corresponding muscles can result in loss of appropriate feedback

    Steadiness - Ability to keep body as motionless as possibleMeasure of postural sway

  • Postural swayDeviation from Center of Pressure, Balance & Vertical Force (CoP, CoB, or CoF)Determined using mean displacement, length of sway path, length of sway area, amplitude, frequency and direction relative to CoP

    Symmetry - Ability to distribute weight evenly between 2 feet in upright stance. Measures:Center of Pressure (CoP)Center of distribution of the total force applied to the supporting surfaceCenter of Balance (CoB)Point between feet where the ball & heel of each foot has 25% of the body weightRelative weight positioningCenter of Vertical Force (CoF)Center of vertical force exerted by the feet against the support surface

  • Balance DisruptionBalance Deficiencies - Inappropriate interaction among 3 sensory inputs

    2 Factors that Disrupt Balance Position of CoG relative to base of support is not accurately sensed Automatic movements required to maintain the CoG are not timely/effective

    In the event of contact, the body must be able to determine what to do in order to control CoGJoint mechanoreceptors initiate automatic postural response

  • Selecting Movement Strategies during Balance DisruptionJoints (Ankle, Knee & Hip) involved allow for a wide variety of postures that can be assumed in order to maintain CoGForces exerted by pairs of opposing muscles at a joint to resist rotation (joint stiffness)Resting position & joint stiffness are altered independently due to changes in muscle activationMyotatic or Stretch Reflex is earliest mechanism for activating muscles due to externally imposed joint rotation

  • Ankle StrategyShifts CoG by maintaining feet & rotating body at a rigid mass about the ankle jointsGastrocnemius or tibialis anterior are responsible for torque production about ankleAnterior/posterior sway is counteracted by gastrocnemius & tibialis anterior, respectivelyEffective for slow CoG movements when base of support is firm & within LOSAlso effective when CoG is offset from center

    Hip StrategyRelied upon more heavily when somatosensory loss occurs & forward/backward perturbations are imposed or support surface lengths are alteredAids in control of motion through initiation of large & rapid motions at the hip with anti-phase rotation of ankleEffective when CoG is near LOS perimeter & when LOS boundaries are contracted by narrower base of support

  • Stepping StrategyUtilized when CoG is displaced beyond LOS Step or stumble is utilized to prevent a fall

    Instance of musculoskeletal abnormalityDamaged tissue result in reduced joint ROM causing a decrease in the LOS & placing individual at a greater risk for fallResearch indicates that sensory proprioceptive function is affected when athletes are injured

  • Assessment of BalanceSubjective AssessmentRomberg Test traditional assessment

    Balance Error Scoring System (BESS)Prentice, 2004, 4th ed.Google Images

  • Semi-dynamic & dynamic tests functional reach teststimed agility testscarioca hop testTimed T-band kicksTimed balance beam walks (eyes open & closed)

  • Objective AssessmentBalance systemsProvide for quantitative assessment & training static & dynamic balanceEasy, practical & cost-effectiveUtilize to assess:Possible abnormalities due to injuryIsolate various systems that are affectedDevelop recovery curves based on quantitative measures in order to determine readiness to returnTrain injured athleteComputer interfaced force-plate technologyVertical position of CoG is calculatedVertical position of CoG movement = indirect measure of postural sway

  • Prentice, 2004, 4th ed.Force plate measuresSteadiness, symmetry, dynamic stabilityTotal force applied to the platform fluctuates due to body weight and inertial effects of body movementForces based on motion of CoGAllows for static & dynamic postural assessmentSingle or double leg stance, eyes opened or closedMoving visual surround for sensory isolation & interaction

  • Dynamic stability - Ability to transfer vertical projection of CoG around a stationary supporting basePerception of safe limit of stabilityUtilization of external perturbationSome are systematic while others are unpredictable & determined via changes in subject sway

    Athlete should maintain their CoP near A-P and M-L midlines

  • Injury & BalanceStretched/damaged ligaments fail to provide adequate neural feedback, contributing to decreased balance & proprioception May result in excessive joint loadingCould interfere with transmission of afferent impulsesAlters afferent neural code conveyed to CNSDecreased reflex excitationCaused via a decrease in proprioceptive CNS inputMay be the result of increased activation of inhibitory interneurons within the spinal cord

    All of these factors may lead to progressive degeneration of joint & continued deficits in joint dynamics, balance & coordination

  • AnklesJoint receptors believed to be damaged during injury to lateral ligamentsLess tensile strength when compared to ligament fibersResults in deafferentation and signaling via afferent pathwaysArticular deafferentation reason behind balance training in rehabilitation

    Orthotic & bracing interventionEnhancement of joint mechanoreceptors to detect perturbations & provide structural support for detecting & controlling sway

    Modify movement strategies to enhance proprioceptive inputAltered biomechanical alignment alters somatosensory transmission

  • Knee InjuriesLigamentous injury has been shown to alter joint position detectionACL deficient subjects with functional instability exhibit this deficit which persist to some degree after reconstructionMay also impact ability to balance on ACL deficient leg

    More dynamic testing may incorporate additional mechanoreceptor input results may be more definitive

  • Head InjuryBalance has been utilized at a criterion variableAdditional testing is necessary in addition to balance & sensory techniquesPostural stability deficitsDeficits may last several days post-injuryResult of sensory interaction problem - visual system not used effectivelyObjective balance scores can be used to determine recovery curves for making return to play decisions

  • Balance TrainingVital for successful return to competition from lower leg injuryPossibility of compensatory weight shifts and gait changes resulting in balance deficits

    Functional rehabilitation should occur in the closed kinetic chain nature of sportAdequate AND safe function in the open chain is critical = first step in rehabilitation

  • Rules of Balance TrainingExercise must be safe & challengingStress multiple planes of motionIncorporate a multisensory approachBegin with static, bilateral & stable surfaces & progress to dynamic, unilateral & unstable surfacesProgress towards sports specific exercisesUtilize open areasAssistive devices should be in arms reach early onSets and repetitions2-3 sets, 15 30 repetitions or 10 of the exercise for 15 30 seconds later on in the program

  • Classification of Balance ExercisesStatic - CoG is maintained over a fixed base of support, on a stable surfaceSemi-dynamicPerson maintains CoG over a fixed base of support while on a moving surfacePerson transfers CoG over a fixed base of support to selected ranges and or directions within the LOS, while on a stable surfaceDynamicMaintenance of CoG within LOS over a moving base of support while on a stable surface (involve stepping strategy)FunctionalSame as dynamic with inclusion of sports specific task

  • Prentice, 2004, 4th ed.Phase INon-ballistic types of drillsStatic balance trainingBilateral to unilateral on both involved & uninvolved sidesUtilize multiple surfaces to safely challenge athlete & maintaining motivationWith & without arms/counterbalanceEyes open & closedAlterations in various sensory informationATC can add perturbationsIncorporation of multiaxial devices Train reflex stabilization & postural orientation

  • Phase IITransition from static to dynamicRunning, jumping and cutting activities that require the athlete to repetitively lose and gain balance in order to perform activityIncorporate when sufficient healing has occurred Semi-dynamic exercised should be introduced in the transitionInvolve displacement or perturbation of CoGBilateral, unilateral stances or weight transfers involvedSit-stand exercises, focus on postural

  • Bilateral Stance ExercisesPrentice, 2004, 4th ed.

  • Prentice, 2004, 4th ed.Unilateral Semi-dynamic exercisesEmphasize controlled hip flexion, smooth controlled motionSingle leg squats, step ups (sagittal or transverse plane)Step-Up-And-Over activitiesIntroduction to Theraband kicksBalance BeamBalance Shoes

  • Phase IIIDynamic & functional types of exerciseSlow to fast, low to high force, controlled to uncontrolledDependent on sport athlete is involved inStart with bilateral jumping drills straight plane jumping patternsAdvance to diagonal jumping patternsIncrease length and sequences of patternsProgress to unilateral drillsPain & fatigue should not be much of a factorCan also add a vertical component to the drillsAddition of implementsTubing, foam rollFinal step = functional activity with subconscious dynamic control/balance

  • Phase III ExercisesPrentice, 2004, 4th ed.

  • ReferencesPrentice, W.E. (2004). Rehabilitation Techniques for Sports Medicine and Athletic Training, 4th ed., McGraw-HillHouglum, P.A. (2005). Therapeutic Exercise for Musculoskeletal Injuries, 2nd ed., Human Kinetics.Kisner, C. & Colby, L. (2002). Therapeutic Exercise Foundations & Techniques, 4th ed., F.A. Davis.http://www.google.com - Images